Compositions of interpolymerized vinyl aromatic hydrocarbons, acrylic acid esters and rubbery butadiene-styrene copolymers and method of making same



United States Patent M COR POSITIONS OF INTERPOLYMERIZED VINYL AROMATICHYDROCARBONS, ACRYLIC ACID ESTERS AND RUBBERY BUTADIENE-STYRENECOPOLYMERS AND METHOD OF MAKING SAME Francis L. Ingley, Midland, andDaniel Moldovan,

Rhodes, Mich., assignors to The Dow Chemical Company, Midland, Mich., acorporation of Delaware No Drawing. Application March 29, 1955 SerialNo. 497,802

8 Claims. (Cl. 260-455) This invention concerns new compositions ofmatter which are interpolymerized mixtures of monovinyl aromatichydrocarbons, acrylic acid esters and copolymers of butadiene andstyrene.

The new compositions are transparent polymeric materials possessing goodtensile and flexural strength, together with high elongation and impactstrength. They can be calendered on rolls to form film or sheet, ormolded by usual compression or injection molding operations, or byextrusion methods, to form plastic articles suitable for a variety ofapplications. The compositions are soluble in usual organic solvents, e.g. benzene,

Y toluene, xylene, methyl ethyl ketone, or mineral spirits.

Solutions of the polymeric materials in a solvent can be cast as layerson glass plates and dried to form film, or applied to wood, metal, orother surfaces and dried to form tough transparent protective films orsurface coatings.

It has been discovered that the interpolymerization of mixtures orsolutions of one or more monovinyl aromatic hydrocarbons of the benzeneseries, one or more lower alkyl esters of acrylic acid and one or morecopolymers of butadiene and styrene, which copolymers are soluble in themonomers and contain ethylenic unsaturation, in proportions ashereinafter defined, results in the formation of transparent orsubstantially transparent polymeric products having good mechanicalproperties such as tensile strength, impact strength, elongation andhardness.

According to the invention the compositions are prepared by dissolvingor dispersing a soluble copolymer of butadiene and styrene, whichcopolymer contains ethylenic unsaturation, in a mixture of monomersconsisting of at least one monovinyl aromatic hydrocarbon, and at leastone ester of acrylic acid and a lower aliphatic alcohol, e. g. ethylacrylate or butyl acrylate, in proportions as hereinafter defined andheating the solution in mass to polymerize the monomers. The monomerscopolymerize with one another and appear to copolymerize at least inpart with the dissolved copolymer of styrene and butadiene whichcontains ethylenic unsaturation to produce a final compositioncontaining the components in chemically combined or interpolymerizedform. A

It is important that the copolymer of butadiene and styrene be soluble,or infinitely swellable, in the monomers, i. e. the monovinyl aromatichydrocarbon and the acrylic acid ester, to form a solution or colloidaldismatic hydrocarbons.

saturated monohyd ployed in preparing the interpolymerized compositionsare unvulcanized copolymers, i. e. they contain ethylenic unsaturationand are soluble in the monomers as previously mentioned.

The copolymers of butadiene and styrene to be employed in preparing thecompositions can be copolymers containing in chemically combined formfrom 40 to percent by weight of butadiene and from 60 to 20 percent ofstyrene. Copolymers prepared from mixtures of from about 60 to 80percent by weight of butadiene. and from 40 to 20 percent of styrene areusually employed. Mixtures of any two or more of the butadienecopolymers, e. g. a mixture of a soluble copolymer of 40 percent byweight of butadiene and 60 percent of styrene and a soluble copolymer ofabout 75 percent of butadiene and 25 percent of styrene which mixture ofbutadiene copolymers forms clear or substantially clear gelfreesolutions with the monomers, can also be used.

Methods of making the butadiene copolymers are well known. Thecopolymers are usually prepared by dispersing a mixture of the monomersin an aqueous solution of an emulsifying agent, then agitating, heatingand copolymerizing the monomers.

The polymerization is accelerated by the addition of catalysts whichprovide oxygen such as hydrogen peroxide, benzoyl peroxide, tert.-butylhydroperoxide, cumene peroxide, potassium persulfate, etc. The catalystis usually employed in amount corresponding to from 0.1 to 2 percent byweight of the materials to be polymerized.

The soluble butadiene copolymers are usually obtained by stopping thecopolymerization short of completion, e. g. when from 70 to percent ofthe monomers are polymerized, then separating the unreacted monomers andrecovering the copolymer from the aqueous colloidal solution or latex inusual ways, such as by coagulation of the latex, washing and drying thecopolymer, or by drying of the latex on heated rolls, or spray dryingthe latex. Mixtures of the butadiene copolymers, when employed, arepreferably obtained by mixing together latexes of the respectivecopolymers and thereafter recovering the polymer from the mixture oflatexes, e. g. by drying the 'mixture and recovering the dried latexsolids.

The soluble butadiene copolymer, or a mixture of two or more of suchcopolymers of butadiene and styrene, is employed in amount sufficient toform with the monomers, i. e. the monovinyl aromatic hydrocarbon and theacrylic acid ester starting materials, a clear or substantially clearsolution or colloidal dispersion containing from 5 to 10, preferablyfrom 6 to 9, percent by weight of the butadiene-styrene copolymer. Theemployment of the butadiene-styrene copolymer in amount less than 5percent by weight of the final composition results in a polymericproduct having low impact strength. The employment of the copolymer inamount greater than 10 percent of the compositions results in formationof final polymeric products which are soft and have poor tensilestrength.

Suitable monovinyl aromatic hydrocarbons are styrene, ortho metaandpara-vinyltoluene, vinylxylene, ethylvinylbenzene,isopropylvinylbenzene, ethylvinyltoluene, or mixtures of any two or moreof such monovinyl aro- Styrene is preferred.

The alkyl ester of acrylic acid to be employed in preparing thecompositionsis an ester of acrylic acid and a aliphatic alcoholcontaining from one to four carbonj atoins in the molecule. Examples ofsuitable acrylic acid-esters are methyl acrylate, ethyl acrylate, propylacrylate or butyl acrylate, or mixtures of any two or more of suchacrylates. Said acrylates have the general formula:

heat-plastified interpolymerized product tends to break down and destroyor solubilize any insoluble gel particles such as are sometimes formedduring the polymerization reaction, and, thus, frequently improves theappearance of the product. The heat-plastified interpolymer productwherein R represents an alkyl radical containing from may be subjectedto SUbatmPSPheHC Pressure Whlle f to four Carbon atoms milled, e. g. oncompounding rolls, so as to facilitate The monovinyl aromatichydrocarbon and the acrylate vaporization of any volatile ingredientstherefrorn durmg starting materials are employed in proportions corretheP fi devolatlhzatlqn and hot'mllhng Opsponding to from 50 to 60 percentby Weight of the mono erations ust mentioned are desirable, but are notrevinyl aromatic hydrocarbon and from 50 to 40 percent qulmd' of theacry1ate Small amounts of additives such as dyes, pigments,

The compositions are prepared by forming a Solution plasticizers,stabilizlng agents, ant1ox1dants, o r fillers, can of the monomers e g.a mixture of equal parts by Weight be incorporated with the resinousCOlTlPOSllIlOIl 1n usual of styrene and ethyl acrylate, containing from5 to 10, Ways by y fl polymer? g f gp preferably from 6 to 9, percent byweight of the butadiene cPmPoundmg r01 and H111 mg t e same e copolymerand heating the: Solution to polymerize the tive, but the presence orabsence of such additives is not monomers required. The additives whenused are usually employed The solution or colloidal dispersion of thecopolymer m g correspmiqmg to from to 10 percent by of butadiene andstyrene in the monomeric materials can ,i t o e d t bt d be prepared byfirst dissolving the butadiene copolymer 6 resnious mterpo pm 61 er as oalga in the monovinyl aromatic hydrocarbon, then adding the m themterpolymenzatlon reactlon. .after 1 acrylate in the desired proportion,or by dissolving the Subjected to 9 the devqlauhzanon mlnmg copolymer ina mixture of the acrylate and the monoor compoundmg m Just mentloned mayP cut or vinyl aromatic hydrocarbon starting materials ground to formparticles or granules thereof, suitable for The starting solution of thebutadiene copolymer in use m q Operatlons'. granular product themonomers is usually prepared at ordinary temperabe 'm or lmecnon'moldedor extruded tures or thereabout, by agitating a mixture of the ingretogg filaged amcles i g h th dients at atmospheric or substantiallyatmospheric pres- 5 P a e i z w i sure, preferably in the absence orsubstantial absence of Pnnclp 0 e myer} as am app 16 u are no air orOxygen to be construed as limiting its scope.

The solution is usually filtered to remove undissolved EXAMPLE 1 gelparticles of the butadiene copolymer, together with In each of a seriesof experiments a copolymer o any .inert solids or impurities dirt 9Scale prio? to 5 approximately 73.5 percent byweight of butadiene and sgg z g sg ggs to produce the mterpolymenzed 26.5 percent of styrene(GR-S type 1006 rubber) was dissolved in a mixture of 50 percent byweight of monog ggz gi 3 5 25 23 3 i r dfg g gg iggzgf fi meric styreneand 50 percent of ethyl acrylate in proporaromatic hydrocarbon and theacrylate in the desired g i g gg g z g ggg f xi g gfi g gg ro ortions.The solution or 011 'd d' ea ed in bulk i. e in the absence or sul astan t i a l zla s end Weight of b-enzoyi pFroXlde polymerization of aninert liqilid medium to polymerize the monomers g m a d ;3o polymhenzefdby eating t e same or ays at and t on or 3 The 01 merization can becarried out at tern t o betwen 60 and 220 C preferabl from 80 to l t ydays at 150 The col-ltalper was smpped'fmm the in the Presence or of acataglst block of polymer, after which it was ground to a granular Thepolymerization is accelerated by the addition of for? stmtable formolfhng' 5 3 of the polymer; catalysts which Provide oxygen. Examples ofsuitable g i compmislon e l test a? s 2 Inc cross sec ion. ese es pieceswere use o tert.-butyl diperphthalate, tert.-butyl perbenzoate, ortert.- I: 3 5 5 3;;gfig ig ifgggffgr fifiggfi fgg gifi m I t er mo dedtest pieces were em- 21; g gs 3 232 a; g g gg but 15 ployed to determinea heat distortion temperature by a The resulting interpolymer productcan be devol l ggz lf lsl of l 9 l 5 il i i ll il ism/18ml. No: o ay ana oc we ar ness 5X) for g. y the Sarge t H8 meltlng temperature thecomposition. Table I identifies the composition by gals: (13119136;rililnialtgnoggnfprgcmpirielsgsugre nmeawtgtsaguitlll glvng theproportronls lndpercent by weiglit of the rubber an monomers emp oye 1npreparing t e same. The chaglcally l j the P Whlle 1t 18 2 heattablealso gives the properties of the compositions. All plastlfied condition.Milling or compounding of the of the compositions formed transparenttest pieces.

Table 1 Starting Materials Product Run No. Ethyl Butadiene- TensileElonga Notched Heat Dis- Rockwell Styrene, Acrylate, Styrene Strength,tion, Per- Impact tortion Hardness,- Percent Percent copolymer,lbs./sq.m. cen Strength, Temp, 15X

Percent ft.-lbs. C.

47. 5 47. 5 5 3, s40 28. s 0. 43 45 47 47 6 3, 780 37. 0 0. 96 49128-172 46. 5 46. 5 7 a, 760 134. 5 1. 28 50 -175 46 46 8 2, 780 157. 02. 31 47 111-160 45 45 10 2, 390 52. 5 1. 74 50 67-145 EXAMPLE 2 In eachof a series of experiments, a copolymer of approximately 73.5 percent byweight of butadiene and 26.5 percent of styrene (GR-S type 1006 rubber)was dissolved in a mixture of 60 percent by weight of monomeric styreneand 40 percent of ethyl acrylate in proportions as stated in thefollowing table. A charge of 500 grams of the solution was polymerizedby heating the same in a sealed container for 7 days at 90 C. and 3 daysat 150 C. The polymeric product was cooled, removed from thecontainerand ground to a granular form. Portions of the composition werecompression molded to form test pieces of A; x /2 inch cross section by4 inches long. The properties for the composition cent byweight ofstyrene and 40 percent of butyl acrylate. The mixture was stirred atroom temperature. A clear slightly viscous solution was obtained. Thesolution, together with 0.05 percent by weight of benzoyl peroxide aspolymerization catalyst, was polymerized by heating the same in a closedcontainer for 7 days at 90 C., and 3 days at 150 C. The polymericproduct was a substantially transparent block. It was ground to agranular form. Portions of the product were compression molded to formtest pieces of x /2 inch cross section. These test pieces were used todetermine properties for the polymeric product employing proceduressimilar to those employed in Example 1. The interpolymerized product hadthe properties:

A charge of 40 grams of a copolymer of about 73.5 percent by weight ofbutadiene and 26.5 percent of styrene was added to 460 grams of amixture of 60 perwere determined employing these test pieces and proce-Tensile strength 1876 lbs/sq. in. dures similar to those employed inExample 1. Table 11 Elongation 161.4 percent. identifies the compositionby giving the proportions in Notched impact strength 4.3 ft.-1bs.percent by weight of the ingredients from which it was Rockwell Hardness(15X) 23-75. prepared. The table also gives the properties of the ColorVery slighthaze. product. All of the compositions formed transparent Weclaim, moldmgs' 1. A resinous transparent polymeric composition of TableII Starting Materials Product Run No. Ethyl Butadienc- Tensile Elonga-Notched Heat Dis- Rockwell Styrene, Aerylate, Styrene Strength, tlon,Per- Impact tortlon Hardness, Percent Percent copolymer, lbs/sq. in.cent Strength, Temp, 15X

Percent fix-lbs. G.

56. 4 37. 0 6 3, 180 30. 9 2. 91-149 55. 2 36. s s 2, 930 25. 0 a. 16 55100-156 54. 6 3e. 4 9 3, 050 29. 2 3. 27 50 87-147 54. 0 3e. 0 10 3, 07012. 2 1. 74 54 76-142 EXAMPLE 3 matter which comprises aninter-polymerized solution of In each of a series of experiments, acharge of g g g ig i igg g 'g gg f g g g lgi g g; grams of a copolymerof approximately 73.5 percent by 1 g p y 40 east one monovinyl aromatichydrocarbon of the benweight of butadiene and 26.5 percent of styrene(GR S type 1006 rubber) was dissolved in 460 grams of a zene series andfrom 50 to 40 percent of at least one ture of monomeric styrene andethyl acrylate in proporester of acryhc and having the general formula:tions as stated in the following table. The solution, tof gether with0.03 percent by weight of benzoyl peroxide as.polymemauon iaialystwas.sealed m a tm'hned wherein R represents an alkyl radical containingfrom one tamer and polymenzed by heating the same for 7 days at to fourcarbon atoms, and from 10 to 5 percent by 90 and 3 days at 150The.polymenc Product weight of at least one soluble unvulcanizedbutadiene was Cooled removed f.rom the Contamer i f to copolymercontaining in chemically combined form from a granular form. Portions ofthe polymeric composition 40 to 80 percent by Weight of butadiene andfrom 60 were compression molded to form test pieces of /s x /2 to 20percent of styrene" inch cross section by 4 inches long. These testpieces A composition as claimed in claim 1, wherein the were used todetermine the properties for the composimonovinyl aromatic hydrocarbonis Styrene tion employing procedufes sfmllar to those ex nployed}n 3. Acomposition as claimed in claim 1, wherein the Example 1. Table IIIldentlfies the composition by givester f acrylic i is ethyl acrylam illgthe Proportions in P Y Weight of stal'tlng 4. A composition as claimedin claim 1., wherein the materials p y in p p s the same The tablebutadiene copolymer is a copolymer containing in chemialso gives theproperties of the product. cally combined form from about to percent byTable III Starting Materials Product Run No. Ethyl Butadiene- TensileElonga- Notched Heat Dis- Rockwell Styrene, Acrylate, Styrene Strength,tlon, Per- Impact tortlon Hardness, Percent Percent Copolyrner,1bs./sq.ln. cent Strength, Temp., 15X

Percent it.-1bs 0.

1 55. 2 36. 8 s ,140 55 1 76 59 -175 2 50.6 41.4 8 2,530 35.4 a 79 5480-146 s 46.0 46.0 8 2,780 157 2 31 47 111-160 EXAMPLE 4 weight ofbutadiene and from about 40 to 20 percent of styrene.

5. A resinous transparent polymeric composition of matter whichcomprises an interpolymerized solution of from 90 to 95 percent byweight of a mixture of monomers consisting of from 50 to 60 percent byweight of styrene and from 50 to 40 percent of ethyl acrylate, and from10 to percent by weight of at least one soluble unvulcanized butadienecopolymer containing in chemically combined form from 40 to 80 percentby weight of butadiene and from 60 to 20 percent of styrene.

6. A composition as claimed in claim 5, wherein the butadiene copolymercontains in chemically combined form about 60 to 80 percent by weight ofbutadiene and from about 40 to 20 percent of styrene.

7. A resinous transparent polymeric composition of matter whichcomprises an interpolymerized solution of from 90 to 95 percent byweight of a mixture of monomers consisting of from 50 to 60 percent byweight of styrene and from 50 to 40 percent of butyl acrylate, and fromto 5 percent by Weight of at least one soluble unvulcanized butadienecopolymer containing in chemically combined form from 40 to 80 percentby weight of butadiene and from 60 to percent of styrene.

8. A method of making a substantially transparent resinous compositionwhich comprises dissolving a solu- 8 I ble butadiene copolymer of fromto 80 percent by weight of butadiene and from 60 to 20 percent ofstyrene in a mixture of monomers consisting of from to percent by weightof at least one monovinyl aromatic hydrocarbon and from 50 to 40 percentof an ester of acrylic acid having the egneral formula:

H2G= 3H( i-0R wherein R represents an alkyl radical containing from oneto four carbon atoms in the molecule, in amount sufficient to form a 5to 10 weight percent solution of the butadiene copolymer in the monomersand thereafter heating the solution at temperatures between 60 and 220C. to polymerize the monomers.

References Cited in the file of this patent UNITED STATES PATENTS 002,123,599 Fikentscher et al July 12, 1938 2,614,089 Harrison et al. Oct.14, 1952 2,694,692 Amos et a1. Nov. 16, 1954

1. A RESINOUS TRANSPARENT POLYMERIC COMPOSITION OF MATTER WHICHCOMPRISES AN INTERPOLYMERIZED SOLUTION OF FROM 80 TO 95 PERCENT BYWEIGHT OF A MIXTURE OF MONOMERS CONSISTING OF FROM 50 TO 60 PERCENT BYWEIGHT OF AT LEAST ONE MONOVINYL AROMATIC HYDROCARBON OF THE BENZENESERIES AND FROM 50 TO 40 PERCENT OF AT LEAST ONE ESTER OF ACRYLIC ACIDHAVING THE GENERAL FORMULA: